forwarding to public list ... sorry if this reply gets there before the
original.
-----Original Message-----
From: Champion, Mike
Sent: Tuesday, May 28, 2002 12:17 PM
To: w3c-ws-arch@w3.org
Subject: RE: Semantics, Web services and the Semantic WEB
> -----Original Message-----
> From: Francis McCabe [mailto:fgm@fla.fujitsu.com]
> Sent: Monday, May 27, 2002 9:57 PM
> To: w3c-ws-arch@w3.org
> Cc: David W. Levine
> Subject: Semantics, Web services and the Semantic WEB
>
Thanks for a very informative post!
One question: you mention that the semantic web builds on predicate logic
....
> predicate logic makes an admirable graph notation and
> Ontology is the discipline that
> has had most to say about these semantic nodes.
but does not try to assert a global set of axioms ...
> One point to note about the Semantic WEB approach that is very
> interesting: viewed as an Ontology building system (which it is)
> the vision is that there will not be a single definitive Ontology,
> or even a single `upper ontology'. Instead, there are likely to
> be many ontologies and many cross links between them: its an
> ontology web rather than an ontology tree.
My (limited, amateurish) understanding of the role of formal logic in human
affairs is that the big challenge is to come up with a consistent set of
axioms on which to perform valid inferences but is rich enough to be of
practical significance. As a practical matter, this has only happened in a
limited number of disciplines, and required centuries of effort. The lack
of consistency renders the exercise utterly futile; for example, the
oft-cited anecdote (or joke, or whatever it really is):
Bertrand Russell mentioned that a false proposition implies any
conclusion. A student raised his hand and said "given that 1 = 0,
prove that you are the Pope". Russell immediately replied,
"Add 1 to both sides of the equation: then we have 2 = 1.
The set containing just me and the Pope has 2 members.
But 2 = 1, so it has only 1 member; therefore, I am the Pope."
So, what hope is there that useful logical inferences could be made using
cross-linked ontologies that have not undergone rigorous scrutiny to ensure
their mutual consistency? Or is the type of inference required to reach
useful conclusions on the semantic web of a more heuristic variety than
textbook logic? For example, if one finds vastly more RDF pathways that
lead to the conclusion that Karol Wotilya is the Pope than one finds that
conclude the Bertrand Russell is the Pope, is that good enough? (FWIW, a
Google search to dig up the Bertrand Russell joke got a lot more hits than a
Google query to find out the current pope's given name!).
> The WS-Arch WG could, and should, make its requirements clear to the
> SWI. It is hard to imagine the W3C having two competing
> technologies for describing semantics.
I personally think that given the state of immaturity of semantic theory and
technology, and given the limitations of RDF and DAML that you mentioned,
that it WOULD be quite appropriate for the W3C to have competing
technologies for describing semantics. This seems like a time for
exploration, and standardization can come when we understand what really
works well. The W3C works best as a forum for coordinated exploration of
promising alternatives in a way that minimizes gratuitous interoperability
differences. It does not work well when it tries to do "computer science by
committee" that immediately leads to standardization.